The present invention relates generally to the art of photoconductive devices and, more particularly, to a method of oxygen glow treatment of a zinc oxide transparent conductor prior to deposition of a thin film silicon hydrogen alloy film onto said conductor layer.
Photoconductive devices generally consist of a photoconductor capable of generating electrical potential upon being exposed to light and contacts which are effective to draw off any electrical current which results from irradiation of the photoconductor. Such devices include photovoltaic devices, more commonly referred to as solar cells, in which the active structure is formed from thin film silicon hydrogen alloy material formed by a glow discharge in silane. U.S. Pat. No. 4,623,601, issued to Lewis, et al on Nov. 18, 1986, discloses several forms of such devices and is hereby incorporated for all purposes. The preferred structure disclosed by Lewis, et al includes a glass substrate, a zinc oxide transparent conductor, a PIN thin film silicon, TFS, photovoltaic structure and a back contact also formed of zinc oxide.
U.S. Pat. No. 4,751,149 issued to Vijayakumar, et al on June 14, 1988, is also incorporated by reference for all purposes. The Vijayakumar, et al patent discloses a preferred method for depositing highly conductive transparent zinc oxide films at a low deposition temperature.
As illustrated by the above referenced patents, considerable work has been done in efforts to improve the performance of TFS type solar cells. In general, this is based on the belief that the manufacturing costs of thin film type structures should ultimately be lower than the classical single crystal type of solar cells. However, the performance of thin film type solar cells, generally measured in terms of efficiency of conversion of sunlight to electricity, is less than that of the single crystal cells. Most research and development work in the thin film type area has therefore been directed toward improvement of cell efficiency.